Conventionally, in an electric car driven only by a motor and a hybrid electric car driven by both an engine and a motor, a direct current supplied from a DC power source is converted to an alternating current supplied to a vehicle drive motor by an inverter. The inverter, for example, as described in Japanese Patent Laid-Open No. 2001-258267 and Japanese Patent Laid-Open No. 2002-369550, is composed of a semiconductor apparatus called a power module or an inverter bridge circuit and a control substrate loading electronic parts such as a capacitor, a drive circuit, an interface circuit, a sensor circuit, a calculator, and a control power source.
The power module has a switching device composed of an IGBT and an MOSFET attached onto an insulating substrate. Between the surface electrode of the switching device and the wiring terminal fixed to an external case for storing the power module, bonding aluminum wires are connected.